Using Threaded Inserts
Why Use Inserts?
Contrary to popular belief, threaded inserts do not necessarily make your fixing stronger, especially when compared to using decent-sized wood screws. However, there are several compelling reasons to use them:
Easy and Professional Assembly
For products like tables with detachable legs, threaded inserts combined with hex head bolts and an Allen key provide an easy and professional assembly solution for customers. This approach mirrors the simplicity of Ikea flat pack setups, which can be especially appreciated by those less skilled in DIY.
No extra tools required.
Professional appearance right out of the box.
Nearly foolproof assembly.
Durability Through Multiple Assembly Cycles
If you anticipate that your item will need to be assembled and disassembled multiple times, threaded inserts are an excellent choice. While a normal wood screw is very strong, repeated screwing and unscrewing can weaken the connection over time. If your product needs to be reassembled more than ten times, threaded inserts might be worth considering.
Why NOT Use Inserts?
While there are clear benefits to using inserts, there are also some drawbacks to consider:
Requires Precise Drilling and Fitting
When building your table, precise drilling is essential. The holes need to be straight and square to the surface. Any misalignment can result in problems when fitting the inserts and attaching the legs.
Misaligned holes can lead to misaligned bolts, which might not fit properly or at all.
Off-center holes in the mounting plate can prevent the bolts from going in, as there's no wiggle room like with wood screws.
Not Necessarily Stronger
While threaded inserts are strong, they often can't match the strength of a decent-sized wood screw in a solid piece of wood.
Risk of Cracked Inserts
Not all inserts are created equal. Common inserts found at local hardware stores are usually made from zinc alloy, which can crack or split when being screwed into wood. This can be disastrous, leaving you with a half-inserted, immovable insert that may require drilling and digging out, potentially damaging the wood and necessitating new holes for the legs.
Types of Inserts
T-Nuts
T-Nuts require a larger drill hole and are hammered into the wood. They are suitable when the insert and the bolt are on opposite sides of the wood and tighten against each other. This generally makes them unsuitable for table leg applications.
T-nut Insert Top Tips!
Avoid T-Nut inserts in furniture applications unless the design allows for installation on the opposite side of the wood to the legs. For a table top, this would mean visible inserts on the surface, which is not desirable.
Screw In Inserts
Once the correct size hole is drilled, the insert is screwed into the wood, creating a strong bond between the insert and the wood.
Screw In Insert Top Tips!
There are many threaded inserts on the market, each with various patented technologies. Here are the main things to look for:
High-Quality Material: Avoid cheaper zinc-alloy inserts, as they are brittle and prone to cracking during installation. If you have more than 10 inserts to fit, at least one is likely to crack, making removal difficult and potentially ruining your project. Instead, opt for plated steel or stainless steel inserts.
Low Profile Flange: Inserts with large top flanges can create gaps between the wooden surface and the leg mounting plate. Ideally, the plate should be pulled down onto the wood, not the insert.
Continuous Thread: This design is stronger than segmented threads, reducing the risk of breaking during installation.
Hex Head: A hex head (Allen key) mount makes assembly easier and ensures proper alignment, which is critical for optimal performance.
Correct Size Hole: The hole should be slightly larger than the solid part of the insert (at the base of the thread). Manufacturers usually provide an ideal drill size, which might be unusual like 8.3mm. It's important to use the suggested size or measure the solid part yourself, ensuring the drill is around 0.1mm larger than the insert.
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